I was in Austin, TX with both of my previous births and had the same doula for both. The first time around she was a relpacement for the original doula I had hired whose husband got transfered about a month before I was due. All said and done I paid a total of about $400 between the two.
By the time I was preg with #2 my doula was now my best friend
and would not let me pay her! She is such a sweetie and I am fervantly praying she can be here for this birth or at least in the days immediately following.
The going rate in CenTx was $300-750 depending on experience and your income. A lot of doula's there did work on a sliding scale depending on your fianances.
A good place to find out what is the going rates in your area is the doula group on yahoo.groups. Just go to the search feature in the groups area and type in doula.